Thanks to Vorsprung durch Technik, making the choice between petrol and diesel engines isn’t as straightforward as it used to be. Engines of both fuel types offer improved power, lower emissions, sporty performance and increased efficiency. Do you prefer the high-torque pulling power of a diesel or the increased response of a petrol engine?
FSI and TFSI are Audi’s innovative, high performance petrol engines and TDI is Audi’s super-efficient diesel engine, read below to find out more.
More output and torque
FSI technology makes it possible to achieve a seemingly improbable combination of lower fuel consumption and enhanced power and performance. FSI direct fuel injection technology brings these benefits to virtually all the petrol engines in the Audi range, in many cases in combination with turbo charging for optimum response.
More power, less fuel
FSI technology increases the torque and output of petrol engines, making them up to 15% more economical and with reduced exhaust emissions. The dimensions and harmonisation of the combustion chamber design, combined with the airflow and injection rate, results in more power being squeezed out of every drop of fuel.
FSI – how it works
With FSI technology, fuel is injected directly into the combustion chamber. The injector regulates the amount of fuel with millisecond precision at injection pressures of between 30 and 110 bar. During the injection process, the evaporating fuel has a significant cooling effect on the cylinder charge. This contributes to improved cylinder charging and enhanced engine output. The cooling effect also helps reduce the engine’s tendency to knock. This reduction means that the compression ratio of FSI engines can be set considerably higher than for engines with conventional injection systems.
The engines of the FSI family are fitted with a two-stage variable intake manifold. The power mode (short duct length) contributes to the high specific power output of the engines at high engine speeds. At low revs, the long duct length setting is selected increasing the maximum torque by more than 15%.
With the aid of a flap system in the intake duct, the in-cylinder flow can be optimally adjusted. In part-load operation, a strong flow ensures low fuel consumption and low exhaust emissions. At full load, the air is drawn in with minimal losses, meaning that torque and output are increased.
Audi is the first manufacturer in the world to combine direct injection FSI technology with forced induction in volume production. The exceptionally broad torque plateau of the TFSI engine on the one hand permits a fuel-efficient driving style with few gearshifts, and on the other hand means that only light accelerator is needed to produce impressive thrust.
TDI engine technology made its debut in 1989. Audi presented the world’s first production car diesel engine with turbo charging, direct injection and electronic management at the Frankfurt Motor Show (IAA). Turbodiesel technology with direct injection went on to become a major success.
Today, Audi TDI engines featuring the latest common rail injection technology are as notable for their power and refinement as they are for their exceptional economy. Their great advantage is plentiful torque that is available from low revs, making for strong and easily accessible performance, coupled of course with remarkable cruising range. This choice blend continues to make TDI variants the most popular in every Audi model range that offers this option.
Common rail system explained
In TDI engines equipped with the common rail system, all cylinders are located on a single high-pressure rail. This rail is an accumulator, which is supplied by a pump and stores the fuel at a pressure of up to 2,000 bar – the equivalent of the weight of a luxury saloon car on the space of one square centimetre.
Thanks to the high pressure and a very fine bore diameter of only one tenth of a millimetre in the nozzle, the injectors achieve very fine atomisation of the fuel. This ensures excellent mixture preparation and highly efficient combustion, which delivers greater power, low emissions and low fuel consumption.